The measuring of structural sections has in the past been accomplished by a variety of means. For instance, gauging systems have utilized optical scanners are penetrating radiation to enable determination of the thickness of a rolled sheet as it is being produced. In general these techniques are one-dimensional in that they offer no two-dimensional information. This precludes the obtaining of accurate information about the conformity of a more complex shape to a given standard. This conformity to a given shape is referred to herein as the "profile" of the shape.
System which yield profile information are extremely useful in the roll forming of various products such as I-beams, channels, sheet piling, and the like, in which the products are produced in a rolling mill, with the product moving at several hundred feet per minute as it is being produced.
As an example, and not by way of limitation, I-beams are produced at a maximum speed of for instance, a thousand feet per minute. There are various critical dimensions which must be achieved during this process in order to maintain conformity to a given standard and to achieve tolerances small enough to minimize the amount of material used and thus minimize the cost of the product. By way of illustration, if in the formation of the I-beam, the weight per foot can be accurately determined in real time, automatic adjustment of the rolling mill is permitted so that the cost of the product can be reduced.
In rolling mills, the shape of the rolled section is controlled manually which, under the best of circumstances, results in a rolled product having a tolerance of about 2.5 percent. This tolerance is obtained through visual inspection of the product as it is being rolled and manual adjustment of the mill, with the 2.5 percent tolerance only achievable by the most experienced of operators.
Automatic control of the rolling process in which the positions of the rollers are automatically controlled is impossible without data to guide the adjustment. This data is extremely difficult to obtain in the type of environment presented by the rolling mill due to the temperature of the environment, amount of vibration which accompanies the manufacture of the rolled product, and the lack of cleanliness of the entire operation.
It will therefore be appreciated that electro-optical devices when utilized in a rolling mill are of limited utility because of the necessity of cleaning the optics at regular intervals. Moreover, during the rolling process the position of the rolled product is difficult to control which makes accurate real time profile measurements almost impossible. Additionally, the so-called "head" which is utilized in detecting structural parameters must be changed in geometric configuration for different sizes and shapes of the article produced.
Profiling with penetrating radiation in the past has been limited to one-dimensional thickness profiling without regard to any two-dimensional qualities or relationships of the rolled product. This gives only limited information about the structure to be profiled.
An example of strip thickness measurement is illustrated in U.S. Pat. No. 4,047,036 in which X-rays penetrate a strip and are detected by an array of detectors, the outputs of which are summed.
An example of electro-optical apparatus for measuring the thickness of a moving strip of material is illustrated in U.S. Pat. No. 3,671,726. Again only one-dimensional characteristics are measured. Electro-optical gauging is also accomplished in U.S. Pat. No. 4,121,292, in which dual cameras and a scanner are utilized. Here the system gauges two orthogonal dimensions of a moving hot bar.
It will be appreciated that the systems described in the above patents do not acquire sufficient data to permit determining the various features of a structural shape and thus, in the case of I-beams for instance, these systems cannot gauge the thickness of the web or various flanges. In the above described systems an accurate picture of the structural shape being produced is not provided, and as a result an accurate estimate of weight per foot cannot be obtained. Moreover, information is not obtainable as to which portions of the structural shape are within tolerance and there is therefore a lack of information as to which of the process parameters to vary.
In particular, in the case of I-beams, merely measuring the gross attenuation does not provide a machine operator with a measure of the thickness of the web or the flanges or indicate to the operator whether to change web thickness or the thickness of specific flanges.